1. Field of the Invention
The present invention relates to a microscope providing high resolution even when visible light is used without using short wavelength light such as ultraviolet light, and providing many choices on observable specimens.
2. Description of the Related Art
Optical microscopes have excellent advantages that they need not be in contact with a specimen, do not require the specimen to be conductive, and enable structural analysis using the dependence of an optical response (absorption, scattering, emission, or the like) from the specimen on a wavelength. However, the optical microscopes have a serious disadvantage that the spatial resolution thereof is substantially limited to the wavelength λ of light.
Conventionally, the following two methods are known to improve the resolution of the optical microscope: (1) use of light of a short wavelength and (2) use of multiphoton absorption. However, the method (1) is disadvantageous in that light of wavelength shorter than 200 nm does not propagate though the air and in that an optical element (lens, prism, and the like) using transmission or refraction cannot be used at a wavelength shorter than 105 nm. Thus, if the resolution is to be improved using light of a short wavelength, the wavelength is limited to about 100 to 200 nm. Further, with the method (2), the specimen must have energy levels which are markedly resonant with n-photon absorption. Consequently, the specimen is extremely limited. In other words, it is difficult to achieve spatial resolution significantly exceeding the wavelength limit.
In recent years, a proposal has been made to improve the spatial resolution of observations using multiple photons in a quantum-mechanically entangled state (see M. C. Teich and B. E. A. Saleh; Ces. cas. fyz., 47(1997) 3-8). However, because this proposal uses the multi-photon absorption of the specimen, it produces problems similar to those with the method (2).
Thus, the conventional methods proposed to improve the resolution of the optical microscopes are disadvantageous in that they have difficulty in greatly improving the resolution without limiting the observable specimens. No practical methods have been known which solve these problems.